The present invention relates, in general, to optical scanning systems and more particularly, to an optical system for reading bar codes on documents such as bank checks or other types of financial documents.
The use of optical bar codes in printing on financial documents is well-established in the banking industry. In processing these documents, optical readers are employed. Ideally, the presence of a bar would be indicated by one of two states, and the absence of a bar would be indicated by the other of two states. Reading of these documents has become a critical requirement due to the limitations found in the printing of the bars on the documents in which the splattering of ink and the smudging of the bar occurs together with the printing of the bars out of a required position. Because of these conditions, prior bar code readers have been unable to process the documents at the desired speed due to failure to sense all of the bars. Further problems include the printing of bars which are not vertical and the skewed condition of the document when in a reading position. In order to reduce the cost of printing coded bars on a document, matrix printers have been employed for printing bars comprising a row of dots and using fluorescent ink to increase the light intensity reflected from the dots. Using a single-slot type read head in reading bars printed by this type of printing process required expensive transport mechanisms to move the document past the read head at a constant speed in order for the bar code reader to detect correctly all of the printed bars. It is therefore a principal object of this invention to provide a bar code reader which enables the read head to provide a valid read operation irrespective of variations in the speed of the document and the printed position of the bars. It is a further object of this invention to provide a bar code reader for accurately detecting the presence of a bar on a document traveling at a relatively high rate of speed. It is another object of this invention to provide a bar code reader which can read bar codes on a document traveling at a high rate of speed whose construction is relatively simple and therefore low in cost.